1. Field of the Invention
The present invention is directed to an apparatus and a method for generating monochromatic X-ray radiation, of the type using an X-ray source, a monochromator and a slit collimator that are arranged relative to one another so that X-rays of a specific energy among the X-rays emanating from the X-ray source are reflected at the monochromator and emerge through the slit of the slit collimator.
2. Description of the Prior Art
Monochromatic X-ray radiation is especially desired particularly in some areas of medical technology, for example in mammography, since it enables the imaging of body details with higher contrast than polychromatic radiation, with which parts of the X-ray spectrum are always absorbed in the patient under examination, thereby increasing the radiation dose for the patient without contributing to the image. A reduction of the dose for the patient therefore can be achieved with monochromatic radiation.
Also, by a designational utilization of monochromatic X-ray radiation at a specific energy, materials such as contrast agents in medical technology are especially well emphasized in an X-ray image. When, for example, iodine is employed as a contrast agent that is injected into the body of a patient, monochromatic radiation with an energy of approximately 33 keV should be employed so that the tissue structures having the iodine appear especially clearly in generated X-ray images.
An apparatus and a method for generating monochromatic X-ray radiation are disclosed in German OS 199 55 848. As can be seen from FIG. 1 herein, which shows an apparatus according to German OS 199 55 848, the apparatus has an X-ray source 1 (merely indicated here), a monochromator 2 as well as a slit collimator 3. The monochromator 2 is arranged at an angle—referred to as the Bragg angle—relative to the focus F of the X-ray source 1 so that only X-rays with a specific energy are reflected at the monochromator 2 at this angle. These X-rays subsequently pass through the slit of the slit collimator 3 and form a fan-shaped, monochromatic X-ray beam 4 having an aperture angle 5. After penetrating an examination subject 6, the X-ray beam 4 is incident on an X-ray detector 7.
Since the aperture angle 5 usually amounts to only approximately 1°, the X-ray source 1, the monochromator 2 as well as the slit collimator 3 must be rotated around an axis 8 intersecting the slit collimator 3 in order to scan the examination subject 6 with the fan-shaped, monochromatic X-ray beam 4 and acquire a planar X-ray image of the examination subject 6. It is disadvantageous that comparatively long exposure times are required.